The "metal stud" fits the CTOOM flash bracket and what else I do not know.
2133xxx would be the first generation 35 Summicron, the 8 element version.
On Tue, 28 Oct 1997, Damian Dlugolecki <damian@europa.com> wrote:
>
>Can someone tell me what is the function of the protruding metal stud on
>the left hand side of my M2 and M3 just above the baseplate? Is it
>intended to accomodate an accessory of some kind?
>
>Some of you refer to generation of 35mm f2 summicrons. Can anyone tell me
>where I could get a breakdown of the generations, their serial #'s and how
>they differ qualitatively. Mine is #2133xxx and I am very happy with it.
>
>thanks
>Damain
>
>
>